Hi.
nice job
I'm not sure but I think there is no reg/stepup. I would say it seems there are mosfets for rail maybe wrong...
for nrf24l01 ic, at aliexpress search for "nrfl2401 qfn" and you will find it.
What are the passive size for radios? Is it a 4layer, I suppose???
too bad, maybe I won't use it as I prefer semtech rfm69&co, a 868mhz antenna layout could be great! (but lowpowerlab is making one so..). In other hand I like to have the radio module so I can route under it, not sure if it's a big economy..
Like you said it's a nice brick, congrats

The break down cost of the board and components is less than USD $5 ( aliexpress component prices mostly) . Can someone share some PCBA service which can also do components sourcing ? with reasonable pricing of course. I would order some 20 - 30 units and may be others could join to make price cheaper.

Expect to pay +$300 as a startup fee for a production run (paid every time a batch is started, for setting SMD machine up etc.). Add to that component costs, and probably 1-2$ per unit for labor (for testing etc.)

Manually mounted, as in hand soldered? 1$ per board? I think that is a very optimistic price!

I've looked through old emails from various smd assembly houses.. I got one that states setup fee for around 140$ (per batch), and then 4-5$ per unit.. add to that stencil price 60$ (Can be used for multiple batches). and don't forget the BOM price as well..

I know that they are spitting out cheap arduino nano's for 1-2$.. but they are probably not quality checked, just smd assembly, bagged and shipped.. (and they probably make 5000 - 50.000 units per batch)

I think that people need to be realistic on what they can get, at what prices..

@hek
Thanks for quick fix
gm2 = gerber mechanic layer2. So there are many variations of file extensions. I think it would be perfect to add ability to attach a file with custom extension or raw zip\rar without extraction.

@Slorf Do not worry. Antenna will work with any board thikness, but with 1.6mm (with current geomerty configuration) it will be optimal. Almost all china nrf modules (I've seen) have non optimal antenna geometry.
PS
I'am sorry I hope dirtypcb will change you order.

@Slorf I've left the package field in bom blank, so you can use any crystal you have. All components on the board are smd, so crystal should be smd too if you have it. But it may be difficult to place smd crystal as Q2 (too small area) and I've placed holes. I have both SMD and THD crystals but I will put holes in Q1 crystal pads in the next version too. Now you can simply mount THD crystal on the pads, it's not difficult.

Great board.
Did you test the performance ? Like number of recieved packets per second ?

Thanks. I've tested stability (for some months without troubles in typical applications) and RF range. I think it doesn't make sense to test performance with low performance mcu, but you can propose the sketch and I test with it.

Hi @Koresh,
Sorry if this is a dumb question but I'm new to this. What's the minimum voltage to power this board? Is it the 1.9V from the NRF?
I'm thinking of building a node with this using a LiPo battery with a protected TP4056 charging module.
If me idea isn't impossible I'd be highly interested to buy some assembled units of this PCB.
Thanks!

@flozsc
Hi. Minimum operating voltage depends on clock frequency. Boards contain standard 16MHz crystal oscillator to full pro mini compatibility. If you use default bootloader and 16Mhz clock frequency, the board will work with a voltage above 2.7v (on the verge of stability). But you can use internal oscillator (custom arduino boards settings, for example 8MHz or 1MHz for lowerst operating voltage) with some limitations (like slower serial). In this case operating voltage should be above 2--2.1v (do not forget a little dropout of LDO regulator).

@Koresh Thanks for your quick reply.
Sleeping sometimes helps. After thinking over it again, I think I'll prepend a step-up converter to 5V behind the battery as most sensors at least require 3.3V or even 5V...
Looking forward to your update on the 20 test boards!

Checking radios as various nodes. Currently working as 2 relay nodes, DHT 22 temperature node and gateway.
All is good . Range 1-2 meters less than NRF24 with big antenna in apartment surrounding.
Digital pins cheeked like in the video: https://youtu.be/00fy9amZnt4
Analog pins tested with generic arduino light sensor. So radios and pins are OK.

oh maybe I didn't understand well, I thought that semtech ic (rfm69) would be onboard?? because if we wire our antenna, I don't see well why not use rfm69 module instead. In case of pcb antenna trace, ic onboard makes more sense imho. but maybe I'm wrong..I thought to give a try to this sometimes ago but had this reflexion,..and good design of pcb antenna trace for 433-915mhz is a lot bigger than 2.4ghz nrf. and smaller trace, lower range..+ need to be tuned for each design (in theory, I'm not expert)
that's cool because koresh is skilled at this lot of thing to learn! so I can't wait to see or try one board!

I got all the parts, but I think the NRF24L01 is the normal version and not the + version, there is no + to be found on the chip.

Would the older NRF24L01 ( without plus ) work on the board ?, or do I have to use the R1 resistor ?
( Resistor 1M ( which package size ) - unnecessary element (R1 can be mounted for backward compatibility with nRF24L01, nevermind)

@Slorf NRF oscillator can work or not (or could stop after some time). If problems appear use any 1m resistor (0402 or 0603 if you can solder it). Do not worry. It is the last stage (after nrf soldering and atmega programming).
Can you provide link to your nrf chip(where you buy it)? I want to check it.

@koresh Just created a light sensor from one of the boards I bought from you. It works great !
I had to do some tweaking with the serial monitor speed from my arduino IDE (I had to double the speed which was set in the code or something)
I also had to press the reset button just before uploading of the sketch started.
Apart from that: Great !
Thanks !

@Sander-Teunissen
Thanks to your responce.
I'm sorry to hear you faced some hardware problem. Of course the board must restart itself. It may be couse of low quality of mounting first boards or it was damaged during delivery
May be you used incorrect usb-ttl converters boards without correct dtr line? I faced them year ago.. it was bad surprise )

Hi,
I aasembled your node, but the radio chip version is not the + one. After burning the MYS bootloader is prints the debug in serial:
60110 TSM:FAIL:RE-INIT
60112 TSM:INIT
60119 !TSM:INIT:TSP FAIL
60123 TSM:FAIL:CNT=7
60125 TSM:FAIL:PDT

Hi,
I aasembled your node, but the radio chip version is not the + one. After burning the MYS bootloader is prints the debug in serial:
60110 TSM:FAIL:RE-INIT
60112 TSM:INIT
60119 !TSM:INIT:TSP FAIL
60123 TSM:FAIL:CNT=7
60125 TSM:FAIL:PDT

Any suggestions?

For not the + version you should mount 1M resistor (R21). And check all soldering points of course.

@qqlapraline Thanks for your attention to this project. A small batch of these boards is ready. Boards are under tests (individually) and almost ready for sale. Unfortunatelly I have "small" technical troubles with ebay but hope to solve them soon. Otherwise you will be able to buy them via paypal directly soon

I have a question, though. Would it make sense to mutualize the Crystal between the NRF and the Atmel ?

(I love to quote myself )

I saw your question the first time, but it is a relatively hard question so I read documentation before writing the answer. I think this is a not good idea, very many inconsistencies. First, NRF24L01+ chip has a requirement:

Input crystal amplitude and current consumptionThe input signal should not have amplitudes exceeding any rail voltage. Exceeding rail voltage excites the
ESD structure and consequently, the radio performance degrades below specification. You must use an
external DC block if you are testing the nRF24L01+ with a reference source that has no DC offset (which is
usual with a RF source).

If you want to be able to share atmega's crystal you must use Full Swing Crystal Oscillator mode (by default arduino uses Low Power Crystal Oscillator mode). You can set this mode without any problems via fuses, but in this case you can't power atmega from 5V (according nrf24L01+ requirement).

However in this case you can't use 16Mhz crystal because 3.3v/16Mhz is overclocked mode for the atmega 328p (I do not say your device will not work, I say atmel do not garantee stability in this case)

As you can see on the latest photo, I didn't solder atmega328p crystals at all and the chip uses an internal oscillator and is powered from 5V